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Set ting-out a Marine Boiler.

Setting-out a Marine Boiler.—We are now in a position
to detail the method of setting out the plates and putting together
of any form of boiler previously described. Taking first the
Marine Boiler: the Draughtsman must make a list of the plates
required, taken from the drawings, for ordering purposes, giving
each a marginal allowance, which will vary from \ in. to \ in.
all round according to thickness of plate. This is necessary, for
the shears at the Rolling Mill leave a rough edge and distress the
plate. Referring to Fig. 311, the plates N, P, Q, and s would be
ordered as 'sketch plates7; coming in roughly sheared to the shape :
G and x might also be cut down at the mill; but the remaining
plates would be ordered to the nearest rectangle. Care must be
exercised to remember flange or lap allowances. The Fox tube
is rolled by special machinery, so must also be 'ordered out'
When received, it must be carefully gauged at every ring, and if
found to be more than a £ in. oval, must be rejected.

Supposing all the plates have been received, we will refer to
the sketches in Figs. 316 and 317, taking the Front plates first.

I. Front Stay Plate.—This is received roughly sheared, as at
i. It is painted with whitening and marked off to drawing, as
shewn by dotted lines, keeping a near the edge to avoid much
planing. Then the curve b is cut out by band saw to give ant
edge for the flanging gauge 2. Flange to gauge, by the pro-
gressive method, Fig. 290, the ends being set as at 3, by the
horizontal ram. Being now considerably strained, the plate is
placed in a furnace, and uniformly, heated to a dull red heat; on
removal it is laid on a flat table, and straightened by wooden*
hammers, then allowed to cool slowly. The edge la is next
planed on the machine in Fig. 285, and a bevel given by setting
as at 4, the angle being i in 8; often this is'given to outer edges-
only. The long edge is planed with* a stroke the full length,,
and the flange 5 with short strokes, the position of the stops Qr
Fig. 285, being altered for the purpose. The Hanged edge is
milled as at 6, with a conical cutter, to obtain caulking inclination,,
a suitable table being provided to give a curvilinear feed.

The rivet holes are now drilled to the extent of one in "every
six, measured along the fitch line, for use in holding the plates
together while drilling in position. In this case the holes along